Scott Mruczkowski, a valuable inside backup, was placed on injured reserve Thursday because of a recent concussion.

That development, and a look at the Chargers' injury list, isn't encouraging for Sunday's game against the visiting Broncos.

Pro Bowl left tackle Marcus McNeill (neck) didn't practice all week and will miss another game.

Right guard Louis Vasquez remains out of practice with a high-ankle sprain. He is doubtful to be in there on Sunday.

Left guard Tyronne Green, who was replacing Pro Bowler Kris Dielman, remains down with a hand injury. He, too, was listed as doubtful after not practicing all week.

Center Nick Hardwick and right tackle Jeromey Clary are the only opening-day starters in a front that hopes to help the Chargers end their five-game skid.

It could be a tall challenge, but this patchwork line was keen last week in not allowing a sack against the aggressive Bears front.

Brandyn Dombrowski will fill in at left tackle. Rookie Steve Schilling and recently signed free agent Tony Moll will grab guard spots.

But the Broncos will counter with pass rushers Von Miller and Elvis Dumervil and this is a Sunday matchup worth watching.

Look for the Chargers to employ tight ends to help outside, and possibly use backs Mike Tolbert and Jacob Hester more because of their pass-protecting abilities.

—They'll fight to the finish, this struggling NFL team that is trying desperately to find a way to win.

The Chargers entertain the surging Denver Broncos on Sunday, needing a victory in the worst way. After losing five straight and starting to lose sight of the AFC West leader, the Chargers promise to keep sailing, even if they've hit their share of icebergs lately.

That's the message veteran linebacker Takeo Spikes, and others, were spinning on Wednesday. But maybe none of the players are move invested in making the playoffs than Spikes.

Spikes is midway through his 15th season, an impressive career which has never seen him reach the playoffs. So when he talks, it was with heart.

"You do have to work harder and all that kind of stuff but if you go out there and think you have to work that much harder or change up a lot of what you are doing then we have been fooling ourselves. We've been living a lie the whole season," he said.

But Spikes did say if each player does more of a little something - watching film, lifting weights, an extra rep - and then it can benefit the squad.

"Something you can work on to take your game to the next level as an individual," he said. "When you do a little bit more you bring up everyone together collectively that we'll be better."

Whatever they do, the Chargers better hurry. They are running out of time, with just six games remaining and only two being against AFC West foes. The first one comes Sunday against the Broncos.

"We are what we are right now, exactly where we are at," Spikes said of the team's 4-6 record. "Do I like it? No. Do I think we can get better? Absolutely, I do.

"I still feel like we can take that next step. We just need a win. I won't say it will cure everything but it would be a big start for us."

There's no time like now for the Chargers to go one of their traditional late-season runs. They might need one to avoid missing the playoffs for the second straight year.

"People talk about running the table, going 10-6," Spikes said. "It sounds good and I would be the first one to tell you. I want to do that, but you can't get to 10-6 unless you get that one this weekend. That is the best way that I can tell you.

"That is the only thing we are focused on. For us, it's a one-game season."

SERIES HISTORY: 104th regular-season meeting. Broncos lead series, 54-48-1; although the Chargers held on to win the first meeting of the season in Denver, 29-24, despite a furious rally led by Tim Tebow. The Chargers have won four straight against the Broncos and nine of their past 11 meetings. With a win Sunday, the Chargers will have swept the Broncos in each of the past two seasons.

NOTES, QUOTES

—WR Bryan Walters, a member of the practice squad, played Tim Tebow in Wednesday's practice. While not left-handed, Walters ran a wishbone type offense while in high school. "It was fun," Walters said. "I learned a few things and it was fun to get back out there." How did he do? "I put one on the ground but I think I did pretty well," he said.

—Much was made of the Chargers' defense being hampered by the Bears getting such good field positions to start their possessions on Sunday. CB Quentin Jammer said that is no excuse. "Regardless of field position, you have to get them stopped," he said. "That's something we're going to have to do from here on out if we want to win a football game. We have to get them stopped wherever they are on the field."

—WR Vincent Jackson is hoping the Chargers fans show up loud and proud on Sunday. Although Denver usually travels well and to be truthful, the local fan base is down on the reeling Bolts. "You know what, we appreciate all the support we can get," he said. "We're going to keep doing our job, going out there and fighting every week and hopefully we'll get all the support we've gotten in the past."

—There seems to be no end in sight of QB Philip Rivers heaving interceptions. He had two more in the loss to the Bears, giving him an NFL-high 17. "It's a different thing," coach Norv Turner said. "I think it was totally different this week, in terms of what happened. Obviously, the last one got away from him. He was trying to throw the ball away, but they laid out and got the interception in the end zone."

—Junior Seau, the 12-time Pro Bowler while playing linebacker for the Chargers, will be inducted into the team's Hall of Fame on Sunday. That it comes against the Broncos is fitting in that the Chargers' lone Super Bowl season of 1994, the year got off to an unpredictable beginning when Seau intercepted a pass from John Elway, in Denver, just as Elway was finishing a comeback. The ball simply slipped from Elway's hand, Seau snatched it and the team held on for 37-34 victory. "I had the misfortune of coaching against him and with here and in Miami," Turner said. "There never been a guy who gave more of himself in terms of competition in helping his team be successful. Obviously he is one of the all-time greats."

—Despite being in the midst of one of their most disappointing seasons in recent memory, nearly the entire Chargers roster turned out Tuesday to participate in the annual blood drive the club helps orchestrate.

—The chance to see the Chargers possibly end their skid and the prospects of watching one of the most polarizing players in NFL history - Tim Tebow - hasn't shown up at the box office. Sunday's game is in jeopardy of being blacked out locally in a TV market which extends into Los Angeles.

BY THE NUMBERS: 4 - The number of games won in 2003 by the Chargers, the last time the team lost five straight games. The Chargers are currently 4-6.

QUOTE TO NOTE:"I probably can't say this much longer, but as rough as it's been, we're still in it." — QB Philip Rivers on finding a silver lining during a five-game skid.

STRATEGY AND PERSONNEL

The Chargers again look for their offensive line depth to reveal itself Sunday.

Rookie Steve Schilling could be plopped into the starting lineup for the second straight week, but in the second different spot.

Schilling started in place of right guard Louis Vasquez (ankle) last week in Chicago. But when left guard Scott Mruczkowski exited with a concussion, Schilling was moved over to left guard.

That catapulted the newest Charger, Tony Moll, into the right guard spot. And with Mruczkowski on injured reserve and Vasquez not expected to play this week, Schilling and Moll could retain their roles for one more week.

Brandyn Dombrowski is another backup being asked to come through. He'll man the critical left tackle spot with Marcus McNeill still sidelined with a neck injury.

Center Nick Hardwick and right tackle Jeromey Clary are the only opening-day starters penciled in, at this time, to trot out with the first unit against the Broncos.

PLAYER NOTES

—RB Ryan Mathews (knee) didn't practice Thursday after being limited on Wednesday. He was able to return to full participation on Friday and is probable to play. Considering his health and recent fumble, he could have a limited role Sunday.

—OLB Shaun Phillips (foot) has missed four games but was able to practice in a limited role Thursday and full-time on Friday. Listed as questionable, there's a chance he goes Sunday, depending on how his foot reacts.

—DE Jacques Cesaire (knee) was able to work as a full participant all week at practice and will be in the rotation on Sunday.

—CB Marcus Gilchrist (knee), after not working at all Wednesday, took part in the entire practice Thursday and Friday but remains questionable.

—LB Bront Bird (ankle) was a full participant and is probable.

GAME PLAN: The Chargers showed life in their passing game against Chicago and should build on that when competing against a Broncos defense which has struggled with throwing attacks.

Philip Rivers did throw two picks Sunday, but there were stretches where he looked the best he has all season. The Chargers would be keen to ride his hot streak and try to distance themselves from the Broncos early, with a passing attack that stretches the field and gets the ball to their best playmaker, Vincent Jackson.

The Chargers need to be cognizant that because of the Broncos' running game, they won't see the ball all that often. So it's imperative to score when they do get possession, and the best way to do that against the Broncos is to heave the ball.

If the Chargers can seize an early lead, it would be a tough climb for the Broncos to get back into the game as their offense isn't built on playing catch-up with a quarterback more suited to run the ball than pass it.

MATCHUPS TO WATCH: Chargers pass-blocking, which showed well last week vs. the Broncos' pass-rushers, which includes standout rookie Von Miller. Despite playing with only two opening-day starters in Chicago, the Chargers supplied some of their best protection of the year; it was the only game this season Rivers wasn't sacked. But that makeshift line has a huge challenge Sunday, with Miller, the second overall pick, showing why he went so high. Miller has 9.5 sacks and is coming off a monster game in the Broncos' win over the Jets: 10 tackles, 1.5 sacks, a forced fumble, four quarterback hits and three tackles for losses. In addition to Miller, the Chargers can't go to sleep on Elvis Dumervil, who usually plays well when seeing this divisional foe. Dumervil has 3.5 sacks, but can go off at any time to help dominate a game - especially with blocking assignments geared toward stopping Miller. The Chargers' backup linemen will be called to duty once again; there also needs to be blocking help from tight ends and running backs staying back to chip.

Chargers run defense, which revealed some grit last Sunday vs. a Broncos running attack led by Tim Tebow. The Chargers' run defense has long been its soft underbelly. Leading up to the Bears' game, the Chargers had allowed at least 134 rushing yards in four of their past five games. That unit will be tested by the Broncos, who churn out nearly 155 rushing yards per game, fourth-best in the NFL. The Chargers are hoping the inside play of linebackers Takeo Spikes, Donald Butler and Na'il Diggs continues its solid play. But the secondary is going to have to supply run support, and with the way the Broncos detest passing, this should be a no-brainer. But the Chargers also must show they can master the trickery and skills of Tebow, as he strings out the run defense in his T-bone approach, deceiving would-be tacklers with his deft ball-handling.

Chargers running game, which produced a critical fumble in the latest game, vs. Broncos run defense — Ryan Mathews is the Chargers' prime back, but he must continue to show he's ready for prime time. Mathews fumbled for the second time this season in the loss at Chicago; the Bears quickly turned it into seven points. But the Chargers aren't sure there days what they are going to get from Philip Rivers (NFL-high 17 interceptions) so they must have their running game at the ready. But Mathews not only coughed up the football, he didn't do much with it when grasping it: a 2.8-yard average on 13 carries, with 23 of his 37 yards coming on one play. Mike Tolbert, who had three rushes last week, could see his role increase. The Broncos are so aggressive in getting after the passer with Von Miller and Elvis Dumervil that running plays directed right at those linebackers could have them over-pursuing to allow the Chargers some big running gains - especially on passing downs. But the Chargers' mix-and-match front line must show its keen in its run-blocking, something that wasn't evident the last time they played.